NodeClockSkew: what to do when it fires

Alert rule

alert: NodeClockSkew
expr: abs(node_timex_offset_seconds) > 0.05
for: 10m
severity: warning

Alert message: Clock drifts from reference ({{ $labels.instance }})

What it means

The system clock differs from the reference time by more than 0.05 seconds (kernel metric node_timex_offset_seconds) for more than 10 minutes.

Common causes

The time synchronisation service is not running, the NTP servers are unreachable (UDP/123 blocked), a virtual machine after a pause or migration.

Diagnostics

timedatectl status
chronyc tracking && chronyc sources -v      # if chrony is used
systemctl status chronyd systemd-timesyncd --no-pager
journalctl -u chronyd -u systemd-timesyncd -n 50 --no-pager

How to fix

Start and enable the synchronisation service (systemctl enable --now chronyd or systemd-timesyncd), check that the NTP servers are reachable, and use chronyc makestep to force an adjustment.

When it is OK to silence

On isolated machines without NTP where time accuracy does not matter (it is better then to disable the rule for those hosts).

Related alerts

• NodeClockNotSynced
• NodeNetworkErrors
• NodeRebooted
• NodeIowaitHigh
• NodeLoadHigh

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